The principal goal of our research is to model prostaglandin biosynthesis. In particular, the question of whether unsaturated peroxy radicals are intermediate in prostaglandin biosynthesis is the focus of our research. With this goal in mind we have demonstrated that unsaturated peroxy radicals will cyclize to give monocyclic peroxides. These monocyclic peroxides inhibit the aggregation of human blood platelets. We are interested then, in structure activity relationships that give active inhibitors of platelet aggregation.